Fluid pressure operable pumping apparatus



FLUID PRESSURE OPERABLE PUMPING APPARATUS 4 June 23, 1970 s. M. MANTON 1 Filed Nov. 21, 1968 M m BY 4 7 ATTORNEYS United States Patent 3,516,763 FLUID PRESSURE OPERABLE PUMPING APPARATUS Stanley Michael Manton, Olton, England, assignor to Joseph Lucas (Industries) Limited, Birmingham, England Filed Nov. 21, 1968, Ser. No. 777,753 Claims priority, application Great Britain, Dec. 18, 1967, 57,327/67 Int. Cl. F15b 13/02 US. Cl. 417-403 4 Claims ABSTRACT OF THE DISCLOSURE A fluid pressure operable pumping device comprising a double acting piston, a load sensitive fiuidic -bi-stable device for switching a source of pressure fluid alternately between a pair of conduits communicating respectively with the opposite ends of the cylinder containing the piston, a pair of non return valves located in said conduits respectively, a pair of control valves each valve having a control element which is actuated by a force developed by the fluid pressure applied to an inlet to prevent flow through a flow path of the valve, the flow path being open by a predominating force acting on the control element as a result of fluid pressure in the flow path, the inlets of the valves being connected respectively to said conduits upstream of said non return valves and the flow paths being connected respectively between the downstream sides of the non return valves and an outlet, the flow path of each valve being connected to the conduit with which its inlet is connected.

T his invention relates to fluid pressure operable pumping devices of the kind comprising a double acting piston to opposite sides of which fluid pressure is applied in turn to produce reciprocatory motion thereof.

The object of the invention is to provide such a device in a simple and convenient form.

According to the invention a device of the kind specified comprises in combination, a load sensitive fluidic bistable device for switching a source of pressure fluid alternately between a pair of conduits communicating respectively with the opposite ends of the cylinder containing the piston, a pair of non return valves located in said conduits respectively and positioned to allow fluid flow from the source to the ends of the cylinder, a pair of control valves, each valve having a control element which is actuated by a force developed by fluid pressure applied to an inlet to prevent flow through a flow path of the valve, the flow path being opened by a predominating force acting on the control element as a result of fluid pressure in the flow path, the inlets of the valves being connected respectively to said conduits upstream of said non return valves and the flow paths being connected respectively between the downstream sides of the non return valves and an outlet, the flowpath of each valve being connected to the conduit with which its inlet is connected.

In the accompanying drawings:

FIG. 1 is a fluid circuit of one exemple of a pumping device in accordance with the invention and FIG. 2 is a fluid circuit of part of the circuit of FIG. 1.

As shown in FIG. 1 of the drawings there is provided a double acting free piston having subsidiary pistons 11 extending from its opposite ends respectively. The free piston 10 is located within a cylinder 12 whilst the subsidiary pistons 11 are located within extensions 13 respectively of the cylinder 12. The combination so far described constitutes a proportioning pump and during the downward movement of the piston as indicated fluid will be discharged from the lower end of the cylinder 12 and also from the lower cylinder 13. The quantities of fluid discharged are in a constant ratio.

Connected to the opposite ends of the cylinder 12 are a pair of conduits 14 and 15 respectively and which communicate through a device 16 with an inlet 17 which is connected to a source of fluid under pressure. In the present instance this fluid is water and for controlling the pressure a constant pressure valve 18 is provided. Intermediate the device 16 and the ends of the cylinder 12, the conduits 14 and 15 are provided with non return valves 19 and 20 respectively. These valves are arranged to permit the flow of water in the direction towards the cylinder but to prevent the return flow of same. In the particular example the non return valves 19 and 20 are free foil diodes. Moreover, on the downstream side of the non return valve 19 and 20 are positioned restrictors 21 respectively.

Also provided are a pair of control valves 22 and 23. Each control valve includes a valve member to one side of which fluid under pressure can be applied from an inlet. Movement of the valve member under the influence of this fluid pressure causes closure of a flow path but fluid pressure in the flow path can develop a predominating force on the valve member to cause opening of the flow path. The inlets of the valves 22 and 23 are connected to the conduits 15 and 14 respectively and the flow path of the control valve 22 is connected between the conduit 15 downstream of the restrictor 21, and an outlet 24. The flow path of the control valve 23 is connected between the conduit 14 at a position downstream of the restrictor 21 and the outlet 24. Moreover, in the outlet there is provided a further restrictor '25. In the particular example the control valves 22 and 23 include free foil elements.

The device 16 comprises a load sensitive fluidic bi-stable device through which flow of water from the inlet 17 is switched alternately between the conduits 14 and 15.

Such devices are well known and an outline of the fluid paths of the device is seen in FIG. 2. From FIG. 2 it will be seen that the device has an inlet 17a which is connected to the inlet 17 and a pair of outlets 14a and 15a which are connected to the conduits 14 and 15 respectively. In addition the device is provided with four further fluid connections but these are for use when forced switching is required between the outlets. In the present example these connections are carried to a drain so that switching between the outlets occurs as a result of blocking of the flow of liquid through one outlet when the piston reaches its extreme position.

In operation water entering the device 16 flows to one or other of the conduits 14 and 15 and as shown in the drawing it is flowing to conduit 14. Valve 19 is opened to permit the flow of water to the upper end of the cylinder 12 and the free piston 10 is forced towards the opposite end of the cylinder. Water discharged from this end of the cylinder flows by way of the control valve 22 to the outlet 24, the non return valve 20 being closed. The pressure of fluid upstream of the non return valve 19 moves the foil of the control valve 23 to prevent flow through its flow path, the pressure drop across the restrictor 21 in the couduit 14 ensuring that the flow path of the control valve 23 remains closed. When the piston 10 reaches the lower end of the cylinder 12 the device 16 responds to the increased pressure in the conduit 14 and switches over so that the water is diverted along the conduit 14. In doing this the non return valve 20 is opened and water is admitted to the lower end of the cylinder 12 to move the free piston upwardly. The foils of the control valves 22 and 23 are moved to their alternative positions and the non return valve 19 is closed. In this manner as long as water under pressure is applied at the inlet 17, the pitson will reciprocate within its cylinder. The restrictor 25 in the outlet is provided to restrict the rate of travel of the free piston and to maintain the pressure within the flow paths of the control valves to ensure efiicient operation thereof.

One use for such a proportioning valve isin an artificial kidney machine where it is required to dilute concentrated dialysate with water before it is used in the dialysis unit. The dialysate is contained in a tank 26 and flows to the cylinders 13 in turn by Way of valves 27 respectively and flows from the cylinders 13 to a mixing tank 28 by Way of valves 29 respectively. The mixing tank 28 receives the water from the outlet 24.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. A fluid pressure operable pumping device of the kind comprising a double acting piston mounted within a cylinder and comprising in combination, a load sensitive fluidic bistable device for switching a source of pressure fluid alternately between a pair of conduits communicating respectively with the opposite ends of the cylinder containing the piston, a pair of non return valves located in said conduits respectively and positioned to allow fluid flow from the source to the ends of the cylinders, a pair of control valves, each valve having a control element which is actuated by a force developed by fluid pressure applied to an inlet to prevent flow through a flow path of the valve, the flow path being opened by a predominating force acting on the control element as a result of fluid pressure in the flow path, the inlets of the valves being connected respectively to said conduits upstream of said non return valves and the flow paths being connected respectively between the downstream sides of the non return valves and an outlet, the flow path of each valve being connected to the conduit with which its inlet is connected.

2. A device as claimed in claim 1 including restrictions respectively disposed in said conduits intermediate the non return valves and the ends of the cylinder.

3. A device as claimed in claim 2 including a restriction disposed in said outlet to control the rate of movement of the piston.

4. A device'as claimed in claim 3 including a further piston connected to said first piston, said further piston being arranged to effect pumping of a second fluid, the two fluids being discharged into a mixing tank.

References Cited UNITED STATES PATENTS 3,208,448 9/1965 Woodward 10349 XR 3,374,863 3/1968 Kozlowski et a1. 1035l XR 3,444,877 5/1969 Atchley 91-3 XR ROBERT M. WALKER, Primary Examiner US. Cl. X.R. 9l3, 318 

